I set up an interface with multiple pages, each shared with different external guests who have "Editor" access to the interface, but not the underlying data. For example, page 1 is shared with all guests, page 2 with guest A, page 3 with guest B, and page 4 with guest C.

Guests can only comment to me, the base creator, and when using "@" they only see themselves and me. Even if multiple guests have "Editor" access to page 1 (which all guests have access to), they cannot comment to each other.